Method for forming dies

ABSTRACT

A die for cutting paperboard material or the like comprises a pair of die plates having coacting cutting elements which partially overlap in the plane of the material to be cut. In making the die plates, a first image representing the critical overlap portion of the cutting elements is utilized to obtain a second and third image each representing a complete cutting element. The second and third image each includes an overlap portion derived from a common image source thereby to facilitate accuracy of registry of two matching die plates ultimately derived from said second and third images.

United States Patent Klemm et al.

[ 51 May 9,1972

[54] METHOD FOR FORMING DIES [73] Assignee: American Can Company, New York, NY.

22 Filed: Mar. 12, 1968 [21] App]. No.: 712,526

52 U.S. Cl ..96/36,96/27 511 lm. Cl. ..G03c 5/04,G03c 5 00 58 FieldofSearch ..96/38.2,41,36, 27

[56] References Cited UNITED STATES PATENTS 3,265,500 8/1966 Lewis ..96/4l 3,341,329 9/1967 Blake ..96/4l Primary Examiner-Norman G. Torchin Assistant E.\'nminerEdward C. Kimlin Attorney-Robert P. Auber, Leonard R. Kohan and Frank J. Jordan [57] ABSTRACT A die for cutting paperboard material or the like comprises a pair of die plates having coacting cutting elements which partially overlap in the plane of the material to be cut. in making the die plates, a first image representing the critical overlap portion of the cutting elements is utilized to obtain a second and third image each representing a complete cutting element. The second and third image each includes an overlap portion derived from a common image source thereby to facilitate accuracy of registry of two matching die plates ultimately derived from said second and third images.

21 Claims, 19 Drawing Figures PATENTEDMAY 9 I912 F/GI/ SHEET 1 BF 4 IHI HI I l NVEN TORS TREVOR HERBERT BLAKE CARL JOHN KLEMM TERRELL RAY STREET RICHARD AUGUST TIETZ BY M16 ATTORNEY METHOD FOR FORMING DIES BACKGROUND OF THE INVENTION This invention relates to a new and improved method of forming cutting, scoring and/or embossing dies, which are of particular value in the formation of paperboard carton blanks. Conventional dies for forming paperboard carton blanks consist of a male die made up of metal knives mounted in wooden furniture and a female die consisting of impressions cut in a paper member. It has been found that many costly and laborious hand operations necessary for producing such conventional dies can be eliminated by the use of coacting, opposed dies formed from unitary metal plates having the working elements of the dies as an integral part thereof raised above the background areas of the die plates. Such dies may be formed economically by removing portions of a thin, metal plate by chemical means to form the background or depressed areas of the plate, leaving cutting and scoring lands standing above the background areas so formed.

An example of cutting, scoring and/or embossing dies of the type to which this invention relates may be found in U.S. Pat. No. 3,142,233, issued July 28, 1964. As disclosed therein, the projecting lands of one die plate cooperate with the projecting lands on another die plate to effect a cutting or scoring of the material therebetween. The cooperating cutting lands overlap somewhat in the plane of the material but they do not touch one another during the cutting operation. The scoring is effected by a land on one die plate which forces the material between two spaced lands on the other die plate.

The die plates are used primarily for forming carton blanks from sheet material and thus the projecting lands are arranged in a pattern corresponding with the shape and formation of the carton blank to be cut and scored. It is necessary to obtain accurate registry between the two cooperating die plates so that the projecting lands on the matching die plates properly I cooperate with one another to effect the desired cutting and scoring operation on the material.

The present invention relates to making dies of the type hereinabove described and is an improvement over the method disclosed in U.S. Pat. No. 3,341,329, issued Sept. 12, 1967. In the aforesaid patent, each of two photographic negatives bearing an image of one of the coacting cutting lands, including the overlapping portions of the cutting lands, was placed in contact with the surface of separate steel plates coated with photosensitive resist composition. The coating on each plate was then exposed to light from a source passing through the image on the negative, thereby to produce an image on the coating which becomes insoluble to the etching solution at the areas where it has been so exposed. After etching, the steel plates defined two coacting, matched die plates, which carried the cutting and scoring elements as raised lands.

In order to obtain the desired cooperative matching of the lands on the two die plates, the orientation of the lands on the male and female die plates have to be reversed relative to one another. Accordingly, in producing matched die plates having multiple, like images, a film sheet bearing a single image may be stepped in one sequential order for the male die plate and in another sequential order for the female die plate to obtain the aforesaid reverse orientation. In other cases, to obtain the reverse orientation, a table on which the coated steel plates are mounted may be inverted so that the stepping of the male and female die plates can be effected in the same sequential order. Differences in the sequential order of stepping and in the structure of the inverting table did not always produce the required high degree of accuracy of spacing between the stepped images due to the inherent inaccuracy of the mechanical mechanisms employed, as will be further discussed in the description of the preferred embodiment. Such inaccuracies between the spacing of the images resulted in inaccurate registry of the two die plates which in turn adversely affected the cutting action of the dies. Further, when it became necessary to make additional die plates, for example upon reorder at a later date, it was necessary to duplicate the time-consuming operation of stepping and repeating onto the photoresist of the die plates, with the possibility of introducing further inaccuracies relative to the die plates previously made.

In the present invention, the step and repeat operation may be performed in the same sequential order for both the male and female die plates without using an inversion table, wherein any inherent inaccuracies in the step and repeat machine are duplicated in the male and in the female die plates to enhance accuracy of registry of the die plates. In addition, the single images are stepped and repeated onto larger sheets of film so that the latter may be preserved for future use toproduce additional die plates without requiring stepping and re'peating,for example when a reorder is received at a later date.

According to the present invention the critical overlapping portion of the cutting elements are derived from a common image source, the latter consisting of a plurality of like images obtained by the step and repeat process. Accordingly, any inherent inaccuracies in the step and repeat process are included in the common image source so that such inherent inaccuracies are duplicated on the male die plate and on the female die plate, thereby to enhance accuracy of registry between the plurality of like images on the coacting die plates.

SUMMARY OF THE INVENTION A die for cutting sheet material comprises a pair of opposed coacting die members each having one of a coacting pair of cutting elements, which partially overlap one another in the general plane of the material being out. In producing such a die, a first image representing the overlapping section of said cutting elements is formed. A second image representing the overlapping sections of said cutting elements is formed in a manner to obtain orientation reversal of the second image relative to the first image. The first and second images are utilized to obtain a third and fourth image respectively, representing the cutting elements of a pair of matched, coacting, die plates. Each of the images representing the cutting elements includes an overlap section derived from a common image source, thereby to facilitate accuracy of registry of the two matched, coacting die plates derived from said images. Where desired, images representing coacting scoring elements are included on the die plates.

' BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a partially completed drawing used in making thedie plates.

FIG. 2 is a partial plan view of the same drawing in FIG. I on which additional markings have been added to complete the drawing.

FIG. 3 is a magnifiedview of the portion of FIG. 1 included within the circle on the latter Figure.

FIG. 4 is a magnified view of the portion of FIG. 2 included within the circle on the latter Figure.

FIG. 5 is a schematic view indicating the various processing steps in making the die plates.

FIG. 6 is a magnified view of a portion of FIG. 2 with the indicating media representing the scoring elements on the lefthand side thereof and the indicating media representing the cutting elements on the right-hand side thereof.

FIGS. 7 and 8 are magnified views of several sheets of film with images thereon generally oriented with the indicating media'in FIG. 6.

FIGS. 9 and 10 are magnified views of several sheets of film and portions of the die plates illustrating the sequential exposure of sheets of film to impose images on thephotoresist of the male and female die plates respectively, the view in FIG. 10 being inverted to maintain consistency of orientation.

FIG. 11 is a cross-sectional view of a part of a pair of opposed coacting die plates in register showing matched cutting and scoring elements thereon.

FIG. .12 is a magnified view of a part of a sheet of film having an image which is imposed onto the photoresist of the male die plate.

FIG. 13 is a magnified view of a part of another sheet of film having an image which is imposed on the photoresist of the male die plate, the image shown in FIG. 12 being superimposed in broken lines.

FIG. 14 is a magnified view of a part of a sheet of film having an image which is imposed on the photoresist of the female die plate. 7

FIG. 15 is a magnified view of part of another sheet of film having an image which is imposed on the photoresist of the female die plate, the image shown in FIG. 14 being superimposed in broken lines.

FIG. 16 is a cross-sectional view of part of a pair of opposed coacting die plates showing matched, scoring elements and also showing, in phantom, the indicating media which represents said scoring elements.

FIG. 17 is a partial view of the indicating media representing the scoring elements shown in FIG. 16.

FIGS. 18 and 19 are magnified views of several sheets of film with images thereon generally oriented with the indicating media in FIG. 17.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated embodiment of the invention is particularly useful in making cutting and scoring die plates which are used in the formation of paperboard carton blanks. For convenience, a pairof die plates, which together comprise a die, will be herein designated as male and female die plates. A portion of a cutting and scoring die having male and female die plates 20 and 22 respectively, is shown in FIG. 11. The male die plate 20. has a baseportion 24 from which a cutting element 26 projects. The cutting element 26 is in the form of a projecting land which isformed integrally with the base portion 24. The male die plate 20 also has a male scoring element 28 projecting from and formed integrally with the base portion 24.

The female die plate 22, which cooperates with the male die plate 20 to effect a cutting and scoring of stock material disposed therebetween, has a pattern of cutting and scoring elements thereon which is related to the pattern of cutting and scoring elements on the male die plate 20. Specifically, the

and thus may have a plurality of like patterns formed thereon. An example of an end use for die plates of this type and a method of operation thereof may be found in U. S. Pat. No. 3,142,233, issued July 28, 1964.

Among other things, the height and width of the male scoring element 28 and the width and depth of the groove between the female scoring elements 34, 36 influence the quality of the score which is formed in a paperboard sheet impression between the dies. The preferred dimensional relationship of the scoring elements is more particularly st forth in U. S. Pat. No. 3,341,329, issued Sept. l2, I967.

The amount of horizontal overlap 0 (FIG. 11) of the coacting cutting elements 26 and substantially affects the cutting operation. If there is too much overlap, the paperboard stock may not be cut satisfactorily. The amount of vertical gap G between the plates 20, 22 (i.e. the closest vertical distance between the working elements of the plates 20, 22 when the press is on impression) also affects the operation of the cutting elements 26, 30. The preferred dimensional relation-ship of the horizontal overlap O and the vertical gap G are more fully set forth in the aforementioned US Pat. No. 3,341,329.

As previously indicated, the amount of overlap O is critical in effecting satisfactory cutting of the paperboard stock. It will be seen, as the description progresses, that provisions are made to provide accurate control of the relative position of the cutting element edges 38 and 40, which edges define the female die plate 22 has a base portion 32 from which a cutting element 30 projects, the latter being adapted to cooperate with the projecting cutting element 26 on the male die plate 20 to effect cutting of the stock material disposed between the die plates 20, 22. As will be further described, the cutting elements 26 and 30 overlap in the'general plane of the stock material to be cut, such overlap being indicated by the letter O in FIG. 1 1. During the cutting operation, the cutting elements 26, 30 project into a portion of the stock material, but the cutting of the stock material is effected without any contact being made between the cutting elements 26 and 30.

The female die plate 22 also includes scoring elements 34, 36 which are integral with the base portion 32 and which are spaced apart so as to receive stock material forced therebetween be the male scoring element 28 on the male die plate 20. The die plates 20 and 22 may be flexible metal plates mounted on rotary cylinders by suitable clamps and, upon rotation, effect cutting and scoring of paperboard stock material advanced therebetween.

The pattern of the cutting and scoring elements on the die plates 20, 22 'is such as to cut a box blank from the stock material and provide score lines thereon so as to permit folding ofthe cut-out box blank into a completed box or carton. The die plates 20, 22 are made to a size and configuration corresponding to the particular design of the box or carton blank desired. Thus. the partial showing in FIG. 11 is representative and illustrates the cutting and scoring elements of only one small section of the die plates. The die plates 20, 22 may cut a plurality of box blanks from the stock material at a given time overlap 0, when the dies are on impression. Accordingly, the edges 38, 40 are sometimes hereinafter referred to as critical edges to distinguish them over the opposite edges 42, 44 of each cutting element 26, 30, respectively, which are not as critical because the overall width of the cutting elements 26, 30 may be of any convenient width consistent with the limitations of available space and the requirements of adequate strength to resist distortion and deformation. The portion of each cutting element 26, 30 not included as part of the overlap O is hereinafter sometimes referred to as the backup and is indicated by B in FIG. 11.

The die plates 20, 22 are formed by an etching process in which the metal plates are etched away except in the areas where the projecting working elements are to be formed. Prior to the etching of the plates 20, 22 any well-known photosensitive-resist coating is placed on the surface thereof. The photosensitive-resist coating is then exposed to light from a light source passing through a photographic negative which carries an image corresponding to the image or pattern of the cutting and scoring elements to be formed on the die plates 20, 22. Since the photographic negative is transparent only at the portions corresponding to the image thereon, a corresponding image is imposed on the resist coating. The area representing the image imposed on the resist coating receives light and becomes insoluble to the etchant which is subsequently applied. After the etching process, those areas of the plates beneath the hardened resist material become the working elements orlands which effect the cutting and scoring of the paperboard, stock material as heretofore described. Allowances are made for undercutting of the resist coating by the etching solution. It is known, for example, that for etching steel, an etching solution containing 20 percent nitric acid will undercut the resist coating approximately 0.010 inch per edge for an etching depth of 0.0 l 5 inch.

The photographic negatives from which the die plates 20, 22 are made are derived from a drawing of a carton blank,

such drawing representing generally the composite working elements of the two die plates 20, 22 with allowance being made for undercutting of the resist coating by the etching solution as previously indicated. According to the illustrated embodiment, the drawing is photographed at an intermediate stage of completion as shown in FIG. 1, and also when it is completed, as shown in FIG. 2.

Referring to FIG. 1, a sheet of material 48'bears a drawing 50 of parts of the composite working elements of the opposed die plates 20 and 22. Drawing 48 may be prepared on a suitable material such as paper or plastic film. Since, however, a

high degree of precision is necessary in the dies produced, it is desirable that the material be one having high-dimensional stability. One example of an appropriate material is polyethylene terephthalate sheet. The lines of drawing 50 may be laid down accurately with an indicating medium such as ink or the like, but, preferably, they are laid down with color tapes of a pre-selected width, including allowances for undercutting, and color. More particularly, the heavier lines (e.g. line 52) in FIG. 1 represent the scoring elements 28, 34, 36 (see FIG. l l) of the male and female die plates 20, 22 while the thinner lines (e.g. line 54) represent the overlap portions 0 of the cutting elements 26, 30 of the die plates. As can be seen in the enlarged portion of drawing 50 in FIG. 3, an indicating medium 56 (e.g. blue tape) represents the female scoring elements 34, 36 of the female die plate 22, and another indicating medium 58 (e.g. red tape) represents the male scoring element 28 of the opposed male die plate 20. Yet another indicating medium 60 (e.g. black tape) represents the areas at which the cutting elements 26, 30 of the two die plates overlap to form areas common to the plan images of both die plate 20, 22. The backup portion B (see FIG. 1 1) of the cutting elements 26, 30 are not shown or represented on drawing 50.

The indicating media 56, 58, 60 are selected such that media 56 and 58 are separable from each other by the use of color filters or the use of sets of different colored lights to illuminate sheet 48 at the time when images therefrom are imposed on a color-sensitive photographic surface, or by the use of photographic films sensitized to some wave lengths but insensitive to others. Indicating medium 60 is such that the optical-photographic techniques used to selectively separate out media 56 and 58 do not separate out medium 60.

In the preferred mode of carrying out the method, media 56 and 58 are of complementary colors which easily can be separated from each other by the use of color filters. Although these colors are indicated in the drawings as being blue and red, many other combinations of complementary colors will immediately be obvious to those skilled in the art, such as red and green, yellow and blue, and orange and purple. The media need not be colors, but one of the media could instead be a composition which fluoresces under given lighting conditions, whereas the other medium might be a particular shade of gray, which could easily be separated by lighting techniques from the fluorescing composition.

Medium 60 is shown in FIG. 1 to be black. However, it should be obvious that many other colors would also be suitable, particularly, in this instance, purple, which is a combination of the blue and red in FIG. 1. It will be understood from the following description that in some cases the third medium will be unnecessary since no overlapping of the working surfaces on the drawing 48 may be needed, for example, when only scoring, and no cutting, is to be performed by the dies. As previously indicated, allowances are made throughout for undercutting of the resist coating by the etching solution.

The aforesaid drawing 50 is multiplied by a sizing factor (e.g. a sizing factor of five), and a camera is set for size reduction by a factor of five. An exposure is made and a photographic negative 62 is obtained of the drawing 50. This photographic negative bears an image of the red tape 58 which represents the male scoring element 28 and an image of the black tape 60 which represents the overlap O of the coacting cutting elements 26, 30. The image of the blue tape 56 representing the female scoring elements 34, 36 is excluded from the photographic negative 62 by use of optical-photographic techniques, for example, by using one or more filters which absorb the color blue. Alternatively, the indicating media 56 (blue tape) representing the female scoring elements 34, 36 may be omitted from drawing 50. In such a case, the aforesaid indicating media 56 would be applied to the drawing when the latter is completed as will be described.

After the aforesaid photographic negative 62 is made, the drawing 50 is completed, the completed drawing being indicated by the numeral 64 in FIG. 2. As will be apparent in the enlargement of drawing 64 in FIG. 4, additional indicating media has been applied so that drawing 64 represents a composite of all the working elements of the dies. Besides the indicating media 56, 58, 60 previously described in connection with drawing 50, drawing 64 also includes additional indicating medium 56 (e.g. blue tape) representing the backup portion B of the cutting element 30 of the female die plate 22, and additional indicating medium 58 (e.g. red tape) representing the backup portion B of the cutting element 26 of the male die plate 20. Thus, in those areas of drawing 64 in which the black indicating medium 60 is sandwiched between the blue and red indicating media 56 and 58 respectively, the composite of the blue and black indicating media 56, 60 respectively, represents the cutting element 30 of the female die plate 22, and the composite of the red and black indicating media 58 and 60 respectively, represents the cutting element 26 of the male die plate 20.

As previously indicated, allowances are made for undercutting and the drawing 64 is multiplied by the sizing factor previously used. Two photographic negatives obtained by a camera set for size reduction by the aforesaid sizing factor are made of drawing 64. One photographic negative 70 bears an imposed composite image of the area indicated by indicating media 58 (red tape) and 60 (black tape). The area indicated by medium 56 (blue tape) is not imposed on photographic negative 70 because it is excluded by means of optical-photographic techniques, for example, by using one or more filters which absorb the color (blue) of medium 56. A second photographic negative 72 bears an imposed composite image of the area indicated by media 56 (blue tape) and 60 (black tape) and is obtained by photographing the drawing 64 and eliminating any image of medium 58 (red tape) by optical photographic techniques, for example, by using one or more filters which absorb the color (red) of medium 58.

From the above description it will be seen that photographic negative 70 bears an image representing the male scoring ele' ment 28 and the cutting element 26 of the male die plate 20 (said latter cutting element 26 being made up of overlap O plus backup B). Photographic negative 72 bears an image representing the female scoring elements 34, 36 and the cutting element 30 of the female die plate 22 (said latter cutting element 30 being made up of overlap 0 plus backup B). The processing of the two negatives 70, 72 along with the previously described photographic negative 62, to obtain the male and female die plates 20, 22 is shown schematically in the flow sheet of FIG. 5.

In the aforesaid description, the photographic negative 62 bears an imposed image representing the overlap 0 (black tape) of the cutting elements 26, 30 and the male scoring element 28 (red tape). Alternatively, the indicating medium 56, or the indicating media 56 and 58, may be omitted from drawing 50 and a photographic image obtained respectively of the overlap 0 (black tape) and of the male scoring element 28 (red tape) without the use of filters or of the overlap 0 (black tape) only. The consequences of this alternative arrangement will be discussed more fully hereinafter.

It will be apparent that making drawings 50 and 64 on an enlarged scale and obtaining a size reduction photographically as the three photographic negatives 62, 70, 72 are made increases the accuracy of the positioning of the working surfaces of the die plates to be produced. Thus, for example, if the accuracy attainable in the method of making drawing 50 and 64 is 0.005 inch, and the size of the imageson negatives 62, 70, 72 is reduced by a factor of 5, the maximum error in the photographically imposed images on negatives 62, 70, 72 will be only: 0.001 inch.

Referring to the flow sheet in FIG. 5, each of the photographic negatives 62, 70, 72 is processed in a manner to produce other negatives from which the die plates 20, 22 are ultimately made. In the first step of their processing, photographic positives 74 and 76 are made from the negatives 70 and 72 respectively, and two identical photographic positives 78, 80 are made from the negative 62. The positives 74, 76, 78, 80 are made by contacting through the base of the respective negative according to known procedures. By contacting through the base of the negative, it is meant that the emulsions of the negatives 62, 70, 72 and the emulsions of the raw film on which the positives 74, 76, 78, 80 are made face upwardly so that the image on thepositives 74, 76, 78, 80 have the same orientation as the images on the respective negatives from which they are derived. This latter fact will be apparent by the fact that the reference indicia R in FIG. on the negatives 62, 70, 72 and positives 74, 76, 78, 80 face in the same direction. In making each positive 74, 76, 78, 80 a point source light is disposed a relatively long distance from the respective negative 62, 70, 72 to minimize the light spread as the light rays from the point source light penetrate the space between the emulsions, said space being occupied by the backing of each of the negatives 62, 70, 72. Accordingly, there is a minimum line growth or parallactic displacement of the image as it is transferred from the photographic negative 62, 70, 72 to its respective positive 74, 76,78, 80. After the positives 74, 76, 78, 80 are made, the negatives 62, 70, 72 are preserved.

Following the processing path in FIG. 5, photo-graphic negatives 82 and 84 are made from the positives 74 and 76 respectively. The positives 74, 76 are contacted, according to known procedures, with the emulsions face-to-face so that the images of the negatives 82, 84 are lateral reversals of the images on the respective positives 74, 76 from which they are derived. Lateral reversal of the images will be apparent by comparing the reference indicia R in FIG. 5 on the respective positives and negatives.

The positives and negatives hereinbefore described are combined in two separate steps, as shown in FIGS. 7 and 8, to make two additional positives 88and 90, respectively. FIG. 6 represents a portion of drawing 64, and the images on the sheets of film in FIG. 7 are generally aligned and oriented with the indicating media shown in FIG. 6.In FIG. 6 the indicating media 56, 58 representing the scoring elements 28, 34, 36 are on the left-hand side, and the indicating media 56, 58, 60 representing the cutting elements 26, 30 are on the right-hand side.

Generally, the object of combining the sheets of film, as

hereinafter described in detail, is to produce a sheet of film having a composite image representing the backup B of the butting elements 26, 30 plus a slight additional width herein identified as light lock. The purpose of the light lock is to facilitate combining the backup B and overlap O at a later stage of the processing of the film sheets as'will become apparent. I, Referring to FIG. 7, threesheets of film 76, 78, 82, all previously described, are arranged in contacting layers above the raw film on which the positive 88is to be made. More specifically, the top sheet of film is positive 76 with its emulsion facing upwardly. Positive 76 bears an image 92 which is a composite of medium 60 representing the overlap O of the cutting elements 26, 30 and medium 56 representing the backup B of the cutting element 30 of the female die plate 22. Positive 76 also bears images 94,v 96, of medium 56 representing the female scoring elements 34, 36 of the female die plate 22. The next sheet of film is the positive 78 with its emulsion facing upwardly. Positive 78 bears an image 98 of medium 60 representing the overlap 0 of the cutting elements 26, 30 and an image 100 of medium 58 representing the male scoring element 28. The next sheet of film is the negative 82 with its emulsion facing downwardly. Negative 82 bears an image 102 which is a composite of medium 60 representing the overlap O of the cutting elements 26, 30 and medium 58 representing the backup B of the cutting element 26 of the male die plate 20. Negative 82 also bears an image 104 of medium 58 representing the male scoring element 28.

When the combined sheets of film shown in FIG. 7 are exposed to an overhead light source, the positive images 94, 96, 100 are effective to block out light from passing through the negative image 104 onto the raw film from which the positive is made. Accordingly, the positive 88 does not bear an image representing the scoring elements 28, 34, 36. If any light does difiuse along the sides of positive images 94, 96, 100 to pass through negative image 104 onto the raw film to impose an image (not shown) on positive 88, said latter image may be removed by opaquing a negative subsequently made from the positive 88.

In contrast to the above, an image representing the cutting elements 26, 30 will be imposed on the raw film 88. Specifically, there will be imposed on positive 88 a composite image 106 having a width equal to the width of medium 58 representing the male backup B of the cutting element 26 plus a light lock L as will be further described. It will be seen that the left-hand edge of positive image 106 corresponds to the left-hand edge of negative image 102 because the emulsions of sheets of film 82 and 88 are face-to-face, and the positive images 92 and 98 are located so as not to block off the light above the left-hand edge of image 102. However, the righthand edge of image 102 does not correspond to the right-hand edge of image 106. This is so because the positive images 92, 98 generally overlie the right-hand edge of image 102, thereby blocking off the overhead light to preclude imposing the righthand edge of image 102 onto the film 88. In contrast to the point light source, previously described, it is preferable to use a light which tends to difiuse and spread somewhat as indicated by the angled arrow 108 'in FIG. 7. It will be seen that the right-hand edge of image 106 isdetermined by the amount of parallactic displacement or light spread as the light rays pass the lefthand edge of positive image 98 through the two sheets of film 78 and 82. The aforesaid light source is selected to spread to the extent of passing at a slight angle as indicated by the angled arrow 108 in FIG. 7 but not to the extent of intersecting the right-hand edge of image 102. Thus, the righthand edge of composite image 106 will lie between the previously mentioned imaginary vertical line (shown in FIG. 7) passing by the left-hand edge of image 98 and the right-hand edge of image 102.

More specifically, the width of image 102 equals the width of medium 60 representing the overlap O of the cutting elements 26, 30 plus the width of medium 58 representing the backup B of the cutting element 26. The portion of image 102 representing the overlap Ois in vertical alignment with the image 98 of positive 78, which image 98 also represents the overlap O of cutting elements 26, 30. Accordingly, it can be seen in FIG. 7 that an imaginary vertical line passing by the left-hand edge of image 98 will divide image 102 into two parts, the right-hand part representing the overlap O and the left-hand part the backup B of cutting element 26. Therefore, it can readily be seen from FIG. 7 that the light lock L represents the amount by which the image 106 exceeds the width of the medium '58 representing the backup B of the cutting element 26. Expressed otherwise, film 88 has an image 106 representing the backup B of cutting'element 26 plus an additional width identified as light lock L. The significance of the light lock L will become apparent as the description proceeds. The width of the light lock L is less than the width of the medium 60 representing the overlap O of cutting elements 26, 30. 9

FIG. 8 shows the combining of sheets of filmto obtain positive 90. As in the case of FIG. 7, three sheets of film 74, 80, 84, all previously described, are utilized to obtain positive 90. More specifically, the top sheet of film is the positive 74 with its emulsion facing upwardly. Positive 74 bears a composite image 110 of medium 60 representing the overlap O of the cutting elements 26, 30 and medium 58 representing the backup B of the cutting element 26 of the male die plate 20. Positive 74 also bears an image 112 of medium 58 representing the male scoring element 28 of the male die plate 20. The next sheet of film is the positive with its emulsion facing upwardly. Positive 80 bears an image 114 of medium 60 representing the overlap O of the cutting elements 26, 30 and an image 116 of medium 58 representing the male scoring element 28. The next sheet of film is the negative 84 with its emulsion facing downwardly. Negative 84 bears an image 118 of a composite of medium 60 representing the overlap O of the cutting elements 26, 30 and medium 56 representing the backup. B of the cutting element 30 of the female die plate 22. Negative 84 also bears images 120, 122 of medium 56 representing the female scoring elements 34, 36 of the female die plate 22.

When the combined sheets of film shown in FIG. 8 are exposed to an overhead source of light, the images 120, 122 of negative 84 will be imposed as positive images 124, 126, respectively, on the film 90. The images 112, 116 on positives 74 and 80, respectively, will not block out light to preclude such transfer of images to film sheet 90.

On the right-hand half of FIG. 8, however, an image 128 representing only a part of image 118 of negative 84 is imposed on film sheet 90. More specifically, the right-hand edge of image 128 corresponds to the right-hand edge of image 118 because the emulsions of sheets of film 84, 90 are face-to-face and the positive images 110 and 114 are located so as not to block off the light above the right-hand edge of image 118. However, positive images 110, 114 of film sheets 74, 80, respectively, generally overlie the lefthand edge of image 118, thereby to block off the overhead light and preclude the transfer of the left-hand edge of image 118 onto raw film 90. Because the light tends to diffuse and spread, as indicated by the angled arrow 130 in FIG. 8, it will be seen that the lefthand edge of image 128 is determined by the amount of parallactic displacement or light spread as the light rays pass from the right-hand edge of positive image 114 through the two sheets of film 80 and 84. Accordingly, following the prior detailed description of FIG. 7, it will be apparent that film 90 (FIG. 8) has an image 128 representing the backup B of cutting element 30 plus an additional width identified as light lock L. The light lock is less than the width of the medium 60 representing the overlap of the cutting elements 26, 30.

The positives 88, 90 obtained from the previously described combining operations shown in FIGS. 7 and 8 respectively, are used to make negatives 132, 134 respectively. Negatives 132, 134 are obtained by contacting according to known procedures, with the emulsions face-to-face so that the image on negatives 132, 134 respectively, are lateral reversals of the images on the positives 88, 90 respectively. Lateral reversal of the images will be apparent by comparing the reference indicia R on the respective positives and negatives. Similarly, a photographic negative 86 is made from one of the positives 78, 80. In the illustrated embodiment, the negative 86 is made from the positive 80.

Since photographic negatives 86, 132, 134 are derived from line drawings 50, 64 which represent a single carton blank, and it is desirable to produce a die that will cut and score a number of carton blanks in a single processing operation, the negatives 86, 132, 134 are photomechanically stepped to produce larger photographic positives 140, 136, 138 respectively, each having a plurality of like images arranged, adjacent to one another. The photomechanical stepping is performed by known methods, for example, by use of a conventional photocomposing machine such as that built and sold by the Rutherford Machinery Division, Sun Chemical Corporation, New York. The stepping is effected with the emulsions face-to-face, and a lateral reversal of the images is obtained on the photographic positives 136, 138 and 140, relative to the respective negatives from which they are made.

In order that the spacing between the plurality of images in photographic positives 136, 138 and 140 correspond as accurately as possible to one another, the positives 136, 138, 140 are obtained by stepping the negatives 132, 134, 86 respectively, on the same photocomposing machine and in the same sequential order. By following this procedure, any inaccuracy in the photocomposing machine is duplicated in all three negatives 136, 138, 140 as to the spacing of the images thereon. For example, the photocomposing machine may utilize a mechanical mechanism (e.g., a rotatable lead screw effecting longitudinal displacement of a block element which is in threaded engagement with the lead screw) to advance or step a carrier (not shown), on which the negative 132 is mounted, from one position to an adjacent position. The same procedure on the same machine is followed in stepping negative 86 and negative 134 between corresponding positions. The same sequential stepping order is followed for stepping the images in a longitudinal and transverse direction in obtaining the positives 136, 138, 140.

In this regard, it is noted that a high degree of accuracy is desirable in obtaining registry of image spacing on the three positives 136, 138, because, as will be described hereinafter, these positives are used to make other photographic negatives which are later combined to make the die plates. By following the same sequential stepping order in making the positives 136, 138, 140, the inherent inaccuracy in the mechanical mechanism of the photocomposing machine is minimized. In contrast, it will be appreciated that the accuracy between a lead screw and a meshing threaded block is such that the lead screw in rotating a prescribed number of turns will advance the block in one direction a predetermined distance and that this can be repeated or duplicated with a high degree of accuracy along the identical portion of the lead screw in advancing the block in the same direction. However, the same predetermined distance will not be obtained with the same high degree of accuracy by rotating the lead screw the same prescribed number of turns in an opposite direction because different faces or sides of the lead screw and threaded block are involved.

After the positives 136, 138 are made, negatives 142, 144 respectively, are made therefrom. Negative 142 is made utilizing an arrangement where the emulsion of positive 136 faces downwardly and the emulsion of the raw film from which the negative 142 is made faces upwardly. A clear spacer, e.g., transparent plastic (not shown) is disposed between the downwardly and upwardly facing emulsions so that the latter are spaced apart an amount equal to the thickness of the spacer. The desirability of using a spacer at this point of the processing will become apparent as the description proceeds. It will be seen that the aforedescribed arrangement results in a lateral reversal of the images on negative 142 with respect to the images on positive 136 as indicated by the reference indicia R in FIG. 5.

The negative144 is made from positive 138 by exposing the raw film of the negative 144 through the base of the positive 138. By contacting through the base of the positive 138, it is meant that the emulsion of the positive 138 and the emulsion of the raw film from which the negative 144 is made both face upwardly so that the emulsions are spaced apart an amount equal to the thickness of the base of positive 138. With the abovedescribed arrangement, there is no lateral reversal of the images on negative 144 with respect to the images on positive 138.

From the above, it will be seen that the images on the negatives 142, 144 are reversed with respect to one another. Further, each negative 142 and 144 was derived from a positive, 136, 144 respectively, each having their emulsions spaced from one another, in one case by a clear, plastic spacer and, in the other case, by the base of the film. In this regard, it is pointed out that the spacer has a thickness equal to that of the base of the film so that any light spread or parallactic displacement will be the same in each case. However, it should be pointed out that a point source light is utilized to minimize the light spread as the light rays from the point source light penetrate the space occupied by the spacer (not shown) between the positive 136 and 142 in one case, and the space occupied by the base of positive 138 in the other case. Accordingly, the light spread is minimal and any resulting line growth of the images as they are transferred from the photographic positives 136, 138 to the photographic negatives 142, 144 respectively are substantially equal.

Returning to the flow sheet in FIG. 5, it will be seen that two photographic negatives 146, 148 are made from the positive 140. The negative 148 is made through the base of positive 140, using the same procedure by which negative 144 was made through the base of positive 138. Accordingly, the

images on negative 148 are obtained without lateral reversal relative to the images on positive 140. On the other hand, the negative 146 is made from positive 140 through a spacer (not shown), using the same procedure by which negative 142 was made from positive 136. Accordingly, the images on negative 146 are lateral reversals of the corresponding images on positive 140. Here again, the two negatives 146, 148 are obtained utilizing a point source light so that the light spread is minimal and any resulting line growth is substantially equal on both negatives 146, 148. It will be observed that negatives 146, 148 are derived from a single positive 140.

As will be described in detail, negatives 142 and 146 are utilized to impose images 154 and 156 (FIG. 9) on the photoresist 150 of the male die plate 20 to ultimately produce the working elements on said male die plate. Similarly, the negatives I44 and 148 are utilized to impose images 158, 160, and 162 on the photoresist 152 (FIG. of the female die plate 22 to ultimately produce the working elements of said female die plate.

Turning to a more detailed consideration of the last mentioned steps, it will be recalled that negative 142 was derived from positive 88 (see FIG. 5) so thatimage 106a (see FIG. 9) on negative 142 corresponds to image 106 on negative 88 (see FIG. 7). Accordingly, image 106a represents the backup B of male cutting element 26 plus light lock L. It will be further recalled that negative 146 was derived from positive 80 and that,

since positive 80 is identical to positive 78, the image 98a (see FIG. 9) on negative 146 corresponds to image 98 on positive 78 (see FIG. 7). Accordingly, image 98a on negative 146 represents the overlap O of the cutting elements 26, 30. Similarly, image 100a on negative 146 corresponds to image 100 on positive 78 (see FIG. 7) so that image 100a represents the male scoring element 28.

The negative 146, with its emulsion down, is placed in contact with the photoresist 150 of male die plate and, by exposure to light, the images 98a, 100a on negative 146 are imposed onto the photoresist 150. FIG. 12 shows a section of negative 146 along with the images 98a, 100a which are imposed on the photoresist 150. Thereafter, negative 146 is removed and, before further processing, negative 142 is placed on the photoresist 150 inaccurate registry with the position of the negative 146 previously placed there. The negative 142 is exposed to light and the image 106a thereon is imposed onto the photoresist 150. Since, it will be recalled, image 106a represents the backup B of the male cutting element 26 plus light lock L, said image 106a will be superimposed with image 98a to the extent of the light lock L. The net effect of this is that the light lock L is double exposed so that the composite image 154 on photoresist 150 represents the backup B of the male cutting element 26 and the overlap O of the cutting elements 26, 30. Expressed otherwise, the composite image 154 is made up of the overlap O as derived from image 98a of negative 146 plus the backup B of male cutting element 26 derived from that portion of image 106a of negative 142 which excludes light lock L. Thus, image 154 represents the male cutting element 26.

Although negative 146 was exposed first onto the photoresist coating 150, negative 142 may be exposed first followed by negative 146 to obtain the same results.

The area on photoresist coating 150 defining images 154 and 156 becomes insoluble to the etching solution. The exposed metal die plate 20 is developed and fixed in a conven- 1 There might be slight inaccuracies in registering the posi- .tion of negative 142 with that'of negative 146 in effecting sequential exposure of said two negatives on photoresist 150,

but such slight inaccuracies may be tolerated. For example, if image 106a was located slightly to the left of that shown in FIG. 13, the width of the composite image 154 would be slightly greater than that shown, but the position of the righthand edge (FIG. 13) of image 154 would remain unchanged. The right-hand edge of image 154 represents the critical edge 38, previously described (see FIG. 11), of the cutting element 26, so that the net effect of the aforesaid slight inaccuracy is to increase the overall width of the cutting element 26 which, as previously explained, can be tolerated to a certain extent without affecting the position of the critical edge 38 of cutting element 26.

Referring to FIGS. 10, 14, and 15, the images 158, 160, and 162 on the photoresist 152 of female die plate 22 are derived from negatives 144, 148 using the same basic procedure just described. More specifically, it will be recalled that negative 144 was derived from positive 90 (see FIG. 5) so that image 128a on negative 144 corresponds to image 128 (FIG. 8) on positive 90. Accordingly, image 128a represents the backup B of female cutting element 30 plus light lock I... Similarly, images 124a, 126b on negative 144 correspond to images 124, 126 on positive 90 so that images 124a, 126a represent the female scoring elements 34, 36. It will be further recalled that negative 148 was derived from positive (see FIG. 5) so that image 114a on negative 148 corresponds to image 114 on positive 80 (see FIG. 8). Accordingly, image 114a represents the overlap O of the cutting elements 26, 30. Similarly, image 116a on negative 148 corresponds to image 116 on positive 80 so thatimage 116a represents the male scoring element 28.

Bearing in mind that the drawing in FIG. 10 is inverted from its true position for orientation, as previously described, the

negative 148, with its emulsion down, is placed in contact with the photoresist 152 of female die plate 22 and, by exposure to light, the image 114a on negative 148 is imposed onto photoresist 152. However, before the negative 148 is placed on the photoresist 152, the image 116a thereon is opaqued so that no part of image 116a is imposed on the photoresist 152. Image 116a represents the male scoring element 28, and the latter is not part of the female die plate 22. It will be recalled that male die plate 20 already has an image, i.e., image 156 (FIG. 9), imposed thereon representing the male scoring ele-' ment 28.

7 FIG. 14 shows a section of negative 148 along with the cutting element 30 plus light lock L, the image 128a will be superimposed with image 1 14a to the extent of the light lock L. The net effect of this is that the light lock L is cancelled out so that the composite image 158 on photoresist 152 represents the backup B of the female cutting element 30 plus the overlap 0 of the cutting elements 26, 30. Expressed otherwise, the composite image 158 is made up of the overlap O as derived from image 114a of negative 148 plus the backup B of female cutting element 30 derived from the portion of image 128a of negative 144 which does not include light lock L. Thus, image 158 represents the female cutting element 30. Although negative 148 was exposed first onto the photoresist coating 152, negative 144 may be exposed first followed by negative 148 to obtain the same results.

The area on photoresist coating 152 defining images 158, 160, and 162 hardens and becomes insoluble in the etching solution. The exposed metal die plate 22 is then processed in the manner previously described for the male die plate 20, whereby the finished die plate 22 bears the female scoring elements 34, 36 and the cutting element 30 as raised lands.

Slight inaccuracies in registering the position of negative 144 with negative 148 in effecting sequential exposure of said two negatives on photoresist 152 may be tolerated for reasons previously described. For example, if image 1280 was located slightly to the left of that shown in FIG. 10, the width of the composite image 158 would be slightly less than that shown, but the position of the left-hand edge (referring to FIG. of image 158 would remain unchanged. The left-hand edge (FIG. 10) of image 158 represents the critical edge 40 of the cutting element 30 so that the net effect of the aforesaid slight inaccuracy is merely to decrease the overall width of the cutting element 30 which, as previously explained, can be tolerated to a certain extent, without affecting the position of the critical cutting edge 40 of cutting element 30.

The die plates 20, 22 may be made of any of a variety of etchable metals such as magnesium, copper, steel, bronze and the like, the choice of the particular metal to be utilized in a given case being determined by the relative importance of various factors such as durability, rapidity and ease of etching, flexibility, economy and other factors. The etching medium used will depend on the particular metal which is to be etched, satisfactory etchants for each of the metals listed as well as other etchable metals being well-known in the art. In general, magnesium is most often etched in a bath composition based primarily on nitric acid while copper, steel, and bronze are customarily etched with ferric chloride etchant compositions, although ammonium persulfate and other oxidizing etchants may also be used. Similarly, the die plates 20, 22 may be of a photopolymerizable plastic composition, such as photosensitized nylon or a photopolymerizable composition of a divinyl ester of a polyethylene glycol or the like.

From the above description it will be observed that the image imposed on the photoresist 150 of male die plate 20 is a lateral reversal of the image imposed on the photoresist 152 of female die plate 22. Accordingly, when one of the die plates is inverted in order to mate with the other die plate in the manner shown in FIG. 11, the cutting and scoring elements will be properly oriented to provide the cutting and scoring action previously described.

It will be observed that lateral reversals of the multiple images on negative 148 relative to the images on negative 146 are obtained by exposing through the backing of the film in one case and through a spacer in the other case, said spacer having substantially the same thickness as the film backing. Accordingly, lateral reversal of the multiple images is derived from a common source (i.e., positive 140) and is obtained with minimal light spread whereby any resulting line growth of the multiple images as they are transferred from positive 140 to negative 146 or from positive 140 to negative 148 is substantially equal. Similarly, by obtaining negative 144 from positive 138 through the base of the film and obtaining negative 142 from positive 136 through a spacer, any resulting line growth is substantially equal in each case.

As can best be seen in FIG. 5, the negatives 146, 148 having multiple, like images imposed thereon are derived from a common stepped positive 140 having a plurality of like images. Accordingly, any slight inaccuracies in the stepping operation in making positive 140 will be duplicated on both negatives 146 and 148. Thus, when the multiple, like images on negatives 146 and 148 are imposed on the photoresist of the male and female die plates respectively, the same inaccuracies are duplicated. It can be seen, therefore, that the image of the overlap O borne on both negatives 146, 148 is imposed on the photoresist of the male and female die plates in a manner to provide accurate registry of the overlap O of the two die plates when they are ultimately mated to perform the cutting operation. Expressed otherwise, the overlap O in the male and female die plates is derived from a common source of multiple, like images, thereby insuring accuracy of registry of the cutting elements of the male and female die plates.

It will be observed that image 100a (FIG. 9) representing the male scoring element 28 is imposed and carried on the negative 146. Thus, images representing the male scoring element 28 and overlap O are borne on a single negative 146. This provides accuracy of relationship between the images of the male scoring element 28 and the overlap O on the photoresist 150 of male die plate 20 independently of the accuracy of registry of the two negatives 142, 146 when they are sequentially exposed onto the photoresist 150.

Alternatively, an image representing the male scoring element 28 may be carried on the negative 142 rather than on negative 146. To obtain this, a negative (not shown) may be made of positive 62 and the image on such negative representing the male scoring element 28 opaqued. Thereafter, positives corresponding to positives 78, may be made from said negative on which the image of the male scoring element 28 was eliminated. In such a case, there would be no image (FIG. 7) representing the male scoring element 28 on positive 78. Thus, a portion of image 104 would be imposed on positive 88. A negative is made of such positive 88 and an opaque material applied over said partial image. Thereafter, the negative with the aforesaid opaque material thereon and negative 82, with the image 102 opaqued, are sequentially double exposed onto a raw film whereby the latter has imposed thereon an image corresponding to image 106 representing the backup B of the male cutting element 26 plus light lock and an image corresponding to image 104 representing the male scoring element 28. The resulting positive is then converted to a negative and the latter stepped to make the multiple image film sheet corresponding to positive 136.

Similar processing steps are followed in the case of the female counterpart represented in FIG. 8 to provide images of the female scoring elements 34, 36 on the negative which is finally stepped to obtain the multiple images on a single sheet of film.

It is preferred, however, to carry image 100a representing the male scoring element 28 on negative 146 for the reasons stated, that is, to provide accurate relationship between the male scoring element 28 and the overlap 0 independent of the registering of the negatives 142, 146 relative to one another when they transfer their images onto the photoresist 150.

It will be recalled that it was suggested, as an alternate embodiment, that the indicating media 56, 58 representing the female and male scoring elements 34, 36, 28 may be omitted from drawing 50 and a photographic image obtained of the indicating medium 60 (black tape) only representing the overlap 0 only. In such a case, the medium 58 representing the male scoring element 28 would not appear as an image on negative 62 or on negative 146 which is derived from negative 62. The indicating media 56 and 58 representing the female and male scoring elements 34, 36, 28 would be added subsequently to be included on drawing 64 so that the image representing the male scoring element 28 would appear on negative 70 and would be carried through to negative 142 from which it is imposed onto the photoresist 150 of male die plate 20.

It will be observed in FIG. 7 that images on positives 76, 78 mask out a portion of the light to obtain the previously described light lock L. As an alternate arrangement, other means of masking may be utilized. For example, opaque material may be utilized to provide the same light blocking effect as that accomplished by positives 76 and 78. However, where the image is intricate and tortuous, it is preferable to obtain the light lock in the manner shown in FIG. 7. The above remarks are also applicable to FIG. 8 in that the light lock in said latter figure may be obtained by the same alternate procedure.

It will be recalled that indicating media on the drawings 50, 64 includes allowance for undercutting of the photoresist coating by the etching solution. In some cases, in allowing for undercutting, the indicating media representing the male and female scoring elements may overlap. To illustrate this, a representation of the indicating media which would be required for the scoring elements, including allowance for undercutting, are shown in phantom in FIG. 16' adjacent the scoring elements which said indicating media represent. The

features in FIG. 16, and also in FIGS. 17 and 19, are similar in many respects to those heretofore shown and described. Accordingly, like parts are identified by similar numerals with the addition of the suffix X, thereby obviating the necessity of extended and repetitive discussion. It will be seen in FIG. 16 that indicating medium 56 representing the female scoring elements 34X, 36X and indicating medium 58 representing the male scoring element 28X overlap. The overlapping portions are represented by the same indicating medium 60 (e.g., black) which is not separated out by the optical-photographic techniques used to selectively separate out media 56 and 58. The indicating media representing the scoring elements 28X,

34X, 36X would appear on drawings 50 and 64 as shown in FIG. 17. FIG. 18 shows the combining of the various sheets of film, and by comparing FIG. 18 with the left-hand side of FIG. 7, it will be seen that the net results obtained are similar in each case. Briefly, the images 94X and 96X on positive 76X correspondto the female scoring elements 36X, 34X, respectively, and each such image represents a composite of indicating media 56 and 60. Image 100x on negative 78X and image 104x on negative 82X correspond to the male scoring element 28X, and each such image represents a composite of indicating media 58 and 60. The positive images 94X, 96X, and 100X block out light from passing through the negative image 104X onto the raw film from which the positive 88X'is made.

If any light does diffuse along the sides of positive images 94X,

96X, 100X to pass through negative image 104x onto the raw film to impose an image (not shown) on positive 88X, said latter image may be removed by opaquing a negative subs'equently made from positive 88X. Turning to FIG. 19, which is analogous to the left-hand half of FIG. 8, the images ll2X and ll6X on positives 74X and 80X respectively, correspond to the male scoring element 28X, and each such image represents a composite of indicating media 58 and 60. The images 120x, 122X on negative 84X correspond to the female scoring elements 36X, 34X, and each such image represents a composite of indicating media 56 and 60. It will be seen that the images 120X and 122X on negative 84X will be imposed as positive images 124X and 126X respectively, on the film 90X. The images 112x and 116X on positives 74X and 80X respectively, will not block out light to preclude such transferring of images to film sheet 90X. Accordingly, it will be seen from the above that the same results are obtained in the arrangement of FIGS. .16 through 19 as in the case of the embodiment hereinbefore described in greater detail.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the steps of the method described and their order of accomplishment without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the method hereinbefore described being merely a preferred embodiment thereof.

We claim:

1. In a method of producing a die comprising a pair of opposed coacting die members each having one of a coacting pair of cutting elements, said cutting elements having sections overlapping one another in the general plane of the material being cut thereby, which method comprises the steps of:

forming a first image representing the overlapping section of said cutting elements;

forming a second image representing the overlapping sec tion of said cutting elements in a manner to obtain orientation reversal of said second image relative to the first image; and

utilizing said first and second images to obtain a third and fourth image respectively representing the cutting elements of a pair of matched, coacting, die members.

2. In a method of producing die members according to claim 1;

comprising exposing a sheet of film through the base thereof and through a spacer onto separate sheets of raw film to obtain orientation reversal of said first and second images leading toward production of a pair of matched, coacting, die plates.

3. In a method of producing die members according to claim 2 wherein the thickness of said spacer and the thickness of the backing on said sheet of film are substantially equal.

4. In a method of producing die members according to claim 1 wherein images representing portions of the cutting elements adjacent the overlapping section are borne on sheets of film;

exposing one of said sheets of film through the base thereof and another of said sheets of film through a spacer onto separate sheets of raw film to obtain relative orientation reversal of said images leading toward production of a pair of matched, coacting, die plates.

5. [ha method of producing coacting die plates each having one of a coacting pair of cutting elements and one of a coacting pair of scoring elements, comprising:

forming a first and second image each having portions of its respective outline in related correspondence with and other portions thereof displaced from related correspondence with the outline of the respective cutting elements of said die plates;

one of said images having sections in related correspondence with one of said scoring elements;

forming a third image in related correspondence with predetermined common parts of the cutting elements;

said third image having sections in related correspondence with another of said scoring elements;

optically transferring said first and second images onto separate photosensitive surfaces;

optically transferring the images of said predetermined common parts onto said photosensitive surfaces in register with its other transferred image, whereby the images of said predetermined common parts predominate over said first and second images as to the portions of outline of the latter images which are displaced from related correspondence with the outline of the respective cutting elements, so that each image imposed on each photosensitive surface is a composite of the two images from which it is derived.

6. The method according to claim 5 wherein one of said coacting pair of scoring elements includes a male scoring element, the longitudinal axis of which is centered on a desired score line to be formed in said sheet material and the other of said coacting pair of scoring elements includes a female scoring element having two raisedareas generally parallel to and having their longitudinal axes slightly and equally spaced on opposite sides of said score line;

said third image also having a section representing said male scoring element whereby the relative location, on one photosensitive surface, of the image representing the male scoring element and the image in related correspondence with predetermined common parts of the cutting elements is independent of the registry of said sequential optical transference of images onto said one photosensitive surface.

7. In a method as set forth in claim 5, wherein said photosensitive surfaces comprise photosensitive plates;

removing by chemical means material from said plates except in regions bearing said imposed images to produce a pair of matched, coacting die plates having the working surfaces as integral parts thereof in the form of raised lands above the background areas of said plates.

8. In a method of producing a die comprising a pair of opposed coacting die members each having one of a coacting pair of cutting elements, said cutting elements having sections overlapping one another in the general plane of the material being cut thereby, which method comprises the steps of;

forming a first image representing the overlapping sections of said cutting elements;

forming a second image representing a section of a cutting element of one die member;

forming a third image representing a section of the cutting element of the other die member;

optically combining said first image and said second image to produce a first composite image representing one cutting element;

optically combining said first image and said third image to produce a second composite image representing the other cutting element;

whereby each composite image representing said pair of cutting elements has a section derived from a common image source representing the overlapping section of said cutting elements.

9. in a method for producing a die for forming a line of severence in a sheet material, said die comprising a pair of opposed, coacting die members, each die member having one of a coacting pair of cutting elements, each of said coacting pair of cutting elements having an overlap portion and a backup portion, said overlap portions overlapping one another in the general plane of the sheet material being cut, the method comprising the steps of:

forming an image representing the overlap portion of the cutting elements,

forming two images, each representing one of the cutting elements,

combining said images to obtain two composite images,

each exceeding the width of the backup of one of the cutting elements;

optically combining each of said composite images with said image representing the overlap in a manner to produce resulting images representing the backup plus overlap of the cutting elements.

10. In a method as set forth in claim 9 further comprising:

stepping and repeating each of said composite images onto separate sheets of film so that each of the latter bears multiple like images thereon;

stepping and repeating said image representing the overlap onto a sheet of film so that the latter bears multiple,'like images;

said sheets of film being optically combined as aforesaid to produce a plurality of like images each representing the backup plus overlap of the cutting elements.

11. In a method as set forth in claim 10 wherein said stepping and repeating steps are effected in the same sequential order.

12. In a method as set forth in claim 9 wherein said images representing each cutting element are born on sheets of film;

exposing one film sheet associated with one of the cutting elements through the base thereof to impose its images onto raw film with the same orientation;

exposing another sheet of film associated with the other cutting element through a spacer onto raw film to obtain lateral reversal of the image;

wherein the images representing the cutting elements imposed on said sheets of raw film are reversed relative to one another leading toward production of a pair of matched coacting die plates.

13. in a method as set forth in claim 9 wherein said image representing the overlap is initially born on one sheet of film;

exposing said latter film sheet through the base thereof to impose the overlap image onto raw film with the same orientation;

exposing said one sheet of film representing the overlap through a spacer onto raw film to obtain lateral reversal of the overlap image;

wherein the images representing the overlap imposed on said sheets of raw film are reversed relative to one another leading toward production of a pair of matched coacting die plates.

14. in a method of producing a die for forming a line of severance in a sheet of material, said die comprising a pair of opposed, coacting die members each having one of a coacting pair of cutting elements, each of said cutting elements having an overlap portion and a backup portion, said overlap portions overlapping one another in the general plane of the sheet material being cut, the method comprises the steps of:

forming a first image representing the overlapping portions of said cutting elements;

forming a second image representing one of the cutting elements;

forming a third image representing the other of the cutting elements;

optically combining said first, second and third images in two separate steps to produce two separate composite images each exceeding the width of the backup of one of the cutting elements by light lock;

optically combining each of said composite images with said image representing the overlap in a manner to cancel out the light lock so that the resulting images represent the backup plus overlap of the cutting elements.

15. In a method as set forth in claim 14 wherein one of said two separate steps of combining said first, second, and third images to produce a composite image comprises,

utilizing the first and second image to block light from predetermined sections of the third image to produce the aforesaid light lock on one of said combined images.

16. In a method for producing a die for working a sheet up of material along a pre-selected pattern of cut lines, said die comprising a pair of opposed coacting die members, each die member having one of a coacting pairof cutting elements, each of said cutting elements having an overlap portion and a backup portion, said overlap portions overlapping each other in the general plane of the sheet material being cut, comprising the steps of:

forming a first drawing having a plan image of the area common to both cutting elements representing said overlapping portions of said cutting elements, said common area being centered on and substantially coincident in length to the desired line of severance to be formed in said sheet material;

completing said drawing to include the plan images of both cutting elements, said drawing being related to the degree of undercutting resulting from chemical removal of material in forming said die;

optically transferring the plan image representing the overlapping portions on the first drawing onto a first sheet of film;

optically transferring the plan image of the first of said cutting elements onto a second sheet of film and the plan image of the second of said cutting elements onto a third sheet of film;

said plan image of the first cutting element being marked on said completed drawing in the combination of a first indicating medium and a second indicating medium,

said plan image of said second cutting element being marked on said completed drawing in the combination of a second indicating medium and a third indicating medium;

the second indicating medium indicating said common area on said first and said completed drawing;

said first and third indicating media being optically separable from each other and said second indicating medium being optically combinable with either of said first and third indicating media under conditions which exclude the other of said first and third media;

optically transferring the images on the first and second,

and the first and third sheets of film, each pair in register with one another, onto separate photosensitive surfaces whereby the images imposed on one photosensitive surface is a composite of the images born on the first and second sheets of film and the images imposed on the other photosensitive surface is a composite of the images born on the first and third sheets of film.

17. The method according to claim 16 wherein one die member has a coacting set of scoring elements including a male scoring element, the longitudinal axis of which is centered on a desired score line to be formed in said sheet material and the other die member has a female scoring element comprising two raised areas generally parallel to and having their longitudinal axes slightly and equally spaced on opposite sides of said score line;

said first drawing including the plan image of said male scoring element;

said plan image of the male scoring element being marked on said first drawing with said first indicating medium;

optically transferring the plan image representing the male score element and the plan image representing the overlapping portions onto said first sheet of film.

18. The method according to claim 16 wherein said first and third indicating media are complementary colors and said exclusion is effected by passing said optical transmission through color filters.

19. The method according to claim 17 wherein said female scoring element is marked on said completed drawing with said third indicating medium;

optically transferring the plan image representing the female score element and the plan image representing one of said cutting elements onto said second sheet of film.

20. The method according to claim 17 wherein one die member has a male scoring element, the longitudinal axis of which is centered on a desired score line to be formed in said sheet material and the other die member has a female scoring element comprising two raised areas generally parallel to and having their longitudinal axes slightly and equally spaced on opposite sides of said score line; 7

said completed drawing including the plan images of said scoring elements; 7

said plan image of the male scoring element being marked on said completed drawing in the combination of said second indicating medium and said third indicating medium.

21. in a method of producing die plates, having coacting cutting elements, comprising:

forming a first and second image each having portions of its respective outline in related correspondence with the outline of respective cutting elements of said die plates;

forming a third image in related correspondence with common overlapping sections of said cutting elements;

optically transferring said first and third, and said second and third images, onto separate photosensitive surfaces whereby the images imposed on one surface is a composite of the first and third images and the image imposed on-the other'surface is a composite of the second and third images. 

2. In a method of producing die members according to claim 1; comprising exposing a sheet of film through the base thereof and through a spacer onto separate sheets of raw film to obtain orientation reversal of said first and second images leading toward production of a pair of matched, coacting, die plates.
 3. In a method of producing die members according to claim 2 wherein the thickness of said spacer and the thickness of the backing on said sheet of film are substantially equal.
 4. In a method of producing die members according to claim 1 wherein images representing portions of the cutting elements adjacent the overlapping section are borne on sheets of film; exposing one of said sheets of film through the base thereof and another of said sheets of film through a spacer onto separate sheets of raw film to obtain relative orientation reversal of said images leading toward production of a pair of matched, coacting, die plates.
 5. In a method of producing coacting die plates each having one of a coacting pair of cutting elements and one of a coacting pair of scoring elements, comprising: forming a first and second image each having portions of its respective outline in related correspondence with and other portions thereof displaced from related correspondence with the outline of the respective cutting elements of said die plates; one of said images having sections in related correspondence with one of said scoring elements; forming a third image in related correspondence with predetermined common parts of the cutting elements; said third image having sections in related correspondence with another of said scoring elements; optically transferring said first and second images onto separate photosensitive surfaces; optically transferring the images of said predetermined common parts onto said photosensitive surfaces in register with its other transferred image, whereby the images of said predetermined common parts predominate over said first and second images as to the portions of outline of the latter images which are displaced from related correspondence with the outline of the respective cutting elements, so that each image imposed on each photosensitive surface is a composite of the two images from which it is derived.
 6. The method according to claim 5 wherein one of said coacting pair of scoring elements includes a male scoring element, the longitudinal axis of which is centered on a desired score line to be formed in said sheet material and the other of said coacting pair of scoring elements includes a female scoring element having two raised areas generally parallel to and having their longitudinal axes slightly and equally spaced on opposite sides of said score line; said third image also having a section representing said male scoring element whereby the relative location, on one photosensitive surface, of the image representing the male scoring element and the image in related correspondence with predetermined common parts of the cutting elements is independent of the registry of said sequential optical transference of images onto said one photosensitive surface.
 7. In a method as set forth in claim 5, wherein said photosensitive surfaces comprise photosensitive plates; removing by chemical means material from said plates except in regions bearing said imposed images to produce a pair of matched, coacting die plates having the working surfaces as integral parts thereof in the form of raised lands above the background areas of said plates.
 8. In a method of producing a die comprising a pair of opposed coacting die members each having one of a coacting pair of cutting elements, said cutting elements having sections overlapping one another in the general plane of the material being cut thereby, which method comprises the steps of; forming a first image representing the overlapping sections of said cutting elements; forming a second image representing a section of a cutting element of one die member; forming a third image representing a section of the cutting element of the other die member; optically combining said first image and said second image to produce a first composite image representing one cutting element; optically combining said first image and said third image to produce a second composite image representing the other cutting element; whereby each composite image representing said pair of cutting elements has a section derived from a common image source representing the overlapping section of said cutting elements.
 9. In a method for producing a die for forming a line of severence in a sheet material, said die comprising a pair of opposed, coacting die members, each die member having one of a coacting pair of cutting elements, each of said coacting pair of cutting elements having an overlap portion and a backup portion, said overlap portions overlapping one another in the general plane of the sheet material being cut, the method comprising the steps of: forming an image representing the overlap portion of the cutting elements, forming two images, each representing one of the cutting elements, combining said images to obtain two composite images, each exceeding the width of the backup of one of the cutting elements; optically combining each of said composite images with said image representing the overlap in a manner to produce resulting images representing the backup plus overlap of the cutting elements.
 10. In a method as set forth in claim 9 further comprising: stepping and repeating each of said composite images onto separate sheets of film so that each of the latter bears multiple like images thereon; stepping and repeating said image representing the overlap onto a sheet of film so that the latter bears multiple, like images; said sheets of film being optically combined as aforesaid to produce a plurality of like images each representing the backup plus overlap of the cutting elements.
 11. In a method as set forth in claim 10 wherein said stepping and repeating steps are effected in the same sequen-tial order.
 12. In a method as set forth in claim 9 wherein said images representing each cutting element are born on sheets of film; exposing one film sheet associated with one of the cutting elements through the base thereof to impose its images onto raw film with the same orientation; exposing another sheet of film associated with the other cutting element through a spacer onto raw film to obtain lateral reversal of the image; wherein the images representing the cutting elements imposed on said sheets of raw film are reversed relative to one another leading toward production of a pair of matched coacting die plates.
 13. In a method as set forth in claim 9 wherein said image representing the overlap is initially born on one sheet of film; exposing said latter film sheet through the base thereof to impose the overlap image onto raw film with the same orientation; exposing said one sheet of film representing the overlap through a spacer onto raw film to obtain lateral reversal of the overlap image; wherein the imageS representing the overlap imposed on said sheets of raw film are reversed relative to one another leading toward production of a pair of matched coacting die plates.
 14. In a method of producing a die for forming a line of severance in a sheet of material, said die comprising a pair of opposed, coacting die members each having one of a coacting pair of cutting elements, each of said cutting elements having an overlap portion and a backup portion, said overlap portions overlapping one another in the general plane of the sheet material being cut, the method comprises the steps of: forming a first image representing the overlapping portions of said cutting elements; forming a second image representing one of the cutting elements; forming a third image representing the other of the cutting elements; optically combining said first, second and third images in two separate steps to produce two separate composite images each exceeding the width of the backup of one of the cutting elements by light lock; optically combining each of said composite images with said image representing the overlap in a manner to cancel out the light lock so that the resulting images represent the backup plus overlap of the cutting elements.
 15. In a method as set forth in claim 14 wherein one of said two separate steps of combining said first, second, and third images to produce a composite image comprises, utilizing the first and second image to block light from predetermined sections of the third image to produce the aforesaid light lock on one of said combined images.
 16. In a method for producing a die for working a sheet up of material along a pre-selected pattern of cut lines, said die comprising a pair of opposed coacting die members, each die member having one of a coacting pair of cutting elements, each of said cutting elements having an overlap portion and a backup portion, said overlap portions overlapping each other in the general plane of the sheet material being cut, comprising the steps of: forming a first drawing having a plan image of the area common to both cutting elements representing said overlapping portions of said cutting elements, said common area being centered on and substantially coincident in length to the desired line of severance to be formed in said sheet material; completing said drawing to include the plan images of both cutting elements, said drawing being related to the degree of undercutting resulting from chemical removal of material in forming said die; optically transferring the plan image representing the overlapping portions on the first drawing onto a first sheet of film; optically transferring the plan image of the first of said cutting elements onto a second sheet of film and the plan image of the second of said cutting elements onto a third sheet of film; said plan image of the first cutting element being marked on said completed drawing in the combination of a first indicating medium and a second indicating medium, said plan image of said second cutting element being marked on said completed drawing in the combination of a second indicating medium and a third indicating medium; the second indicating medium indicating said common area on said first and said completed drawing; said first and third indicating media being optically separable from each other and said second indicating medium being optically combinable with either of said first and third indicating media under conditions which exclude the other of said first and third media; optically transferring the images on the first and second, and the first and third sheets of film, each pair in register with one another, onto separate photosensitive surfaces whereby the images imposed on one photosensitive surface is a composite of the images born on the first and second sheets of film and the images imposed on the other photosensitive surface is a composite of the images born on the first and third sheets of film.
 17. THe method according to claim 16 wherein one die member has a coacting set of scoring elements including a male scoring element, the longitudinal axis of which is centered on a desired score line to be formed in said sheet material and the other die member has a female scoring element comprising two raised areas generally parallel to and having their longitudinal axes slightly and equally spaced on opposite sides of said score line; said first drawing including the plan image of said male scoring element; said plan image of the male scoring element being marked on said first drawing with said first indicating medium; optically transferring the plan image representing the male score element and the plan image representing the overlapping portions onto said first sheet of film.
 18. The method according to claim 16 wherein said first and third indicating media are complementary colors and said exclusion is effected by passing said optical transmission through color filters.
 19. The method according to claim 17 wherein said female scoring element is marked on said completed drawing with said third indicating medium; optically transferring the plan image representing the female score element and the plan image representing one of said cutting elements onto said second sheet of film.
 20. The method according to claim 17 wherein one die member has a male scoring element, the longitudinal axis of which is centered on a desired score line to be formed in said sheet material and the other die member has a female scoring element comprising two raised areas generally parallel to and having their longitudinal axes slightly and equally spaced on opposite sides of said score line; said completed drawing including the plan images of said scoring elements; said plan image of the male scoring element being marked on said completed drawing in the combination of said second indicating medium and said third indicating medium.
 21. In a method of producing die plates, having coacting cutting elements, comprising: forming a first and second image each having portions of its respective outline in related correspondence with the outline of respective cutting elements of said die plates; forming a third image in related correspondence with common overlapping sections of said cutting elements; optically transferring said first and third, and said second and third images, onto separate photosensitive surfaces whereby the images imposed on one surface is a composite of the first and third images and the image imposed on the other surface is a composite of the second and third images. 